another_lambda.sh

#!/bin/bash

apply1() (
	body=$2
	block() {
		eval "$body"
	}
	block "$1"
)

apply2() (
	body=$3
	block() {
		eval "$body"
	}
	block "$1" "$2"
)

touch file_a

apply1 file_a "$(cat <<-EOF
	echo "Copying \$1 to file_copy"
	cp \$1 file_copy
EOF
)"

apply2 file_copy file_b "$(cat <<-EOF
	echo "Copying \$1 to \$2"
	cp \$1 \$2
EOF
)"

lambda="$(cat <<-EOF
	echo "Copying \$1 to \$2"
	cp \$1 \$2
EOF
)"

apply2 file_b file_c "$lambda"

rm file_*

bash_lambda.sh

#!/bin/bash

# Functions with lambda/closure passed into as second argument

run_task () {
	echo "  - $1"
	eval "$2"
	if [ $? -eq 0 ]; then
		echo "    [done]"
	else
		echo "    [failed]"
		exit -1
	fi
}

run_grouped () {
	echo "  - $1"
	eval "$2"
	echo "    [done]"
}

run_subtask () {
	echo "    - $1"
	eval "$2"
	if [ $? -eq 0 ]; then
		echo "      [done]"
	else
		echo "      [failed]"
		exit -1
	fi
}

# Passing lambdas into functions

run_task "create file_a" "$(cat <<-TASK
	touch file_a
TASK
)"

run_grouped "create file_b and file_c" "$(cat <<-GROUPED

	run_subtask "create file_b" "$(cat <<-TASK
		touch file_b
	TASK
	)"

	run_subtask "create file_c" "$(cat <<-TASK
		if [ ! -d dir_a/dir_b ]; then
		  mkdir dir_a/dir_b -p
		fi
		touch dir_a/dir_b/file_c
	TASK
	)"

GROUPED
)"

# Unfortunatelly <<- requires tabs :/